Compressors that compress gases and supply the compressed gases to machines or the like connected downstream have been known. As the compressors, there is a compressor in which an inlet guide vane is disposed upstream and a gas is caused to flow in from an inlet to a compressor body via the inlet guide vane. By adjusting an opening degree of the inlet guide vane, a flow rate of the gas flowing in the compressor body is controlled.
In such a compressor, compressor bodies on a plurality of stages are provided from the upstream side of flow of a gas to the downstream side thereof in some cases (for example, see Patent Literature 1). There is also a compressor in which, to increase a flow rate, a plurality of compressor bodies are provided furthest upstream, gases compressed by the plurality of compressor bodies are merged, and subsequently the merged gases are caused to flow in a compressor body located downstream. In such a compressor, there is a control method of controlling the state of a discharged gas by controlling opening degrees of inlet guide vanes provided in the inlets of the plurality of compressor bodies located furthest upstream in a synchronized manner.